1. Technical Field
This invention relates to the catalyzed preparation of trialkylsilyl ethers.
2. Technical Background
The trialkylsilyl ethers of this invention, as well as the trialkylsilyl and carbonyl compounds which are used to prepare the trialkylsilyl ethers of this invention, are well known in the art.
Rasmussin, "O-Silylated Enolates-Versatile Intermediates For Organic Synthesis", Synthesis, 91 (1977), especially pages 91-96, provides a review of silyl enol ethers and ketene silyl acetals, their preparation and reactions. The addition of allylsilanes to aldehydes and ketones in the presence of Lewis acids to form trialkylsilyl ethers is discussed by Dunogues, Chemtech (6), 373 (June 1982). Cross-Aldol reactions of silyl enol ethers with carbonyl compounds, activated by titanium tetrachloride, can be carried out under mild conditions, according to Mukaiyama et al., J. Am. Chem. Soc. 96, 7503 (1974). In a related later paper, Chem. Letters, 163 (1976), Saigo et al. discuss the Michael-type reaction of O-silylated ketene acetals with .alpha.,.beta.-unsaturated carbonyl compounds, promoted by titanium tetrachloride. Nakamura et al., J. Am. Chem. Soc. 98, 2346 (1976) disclose the reaction of ethyl trimethylsilylacetate and tetra-n-butylammonium fluoride with various aromatic and alicyclic ketones and alcohols, and Noyori et al. and Kuwajima et al., J. Am. Chem. Soc. 99, 1265 (1977), describe fluoride ion catalyzed reactions of trimethylsiloxycyclohexenes and benzaldehyde. In J. Am. Chem. Soc. 104, 1025 (1982) Kuwajima et al. describe fluoride ion catalyzed reactions of trimethylsiloxyolefins and alkyl halides.
The alkylation of trimethylsiloxyolefins in the presence of tris(diethylamino)sulfonium difluorotrimethylsilicate as a fluoride ion source is discussed by Noyori et al. in Tetrahedron Letters 21, 2085 (1980). Clark, Chem. Rev. 80, 429 (1980), "Fluoride Ion as a Base in Organic Synthesis," discloses on page 441 aldol-type reactions of trimethylsiloxyolefins and aldehydes in the presence of a fluoride ion source, such as tetraalkylammonium fluoride.
Colvin, "Silicon in Organic Chemistry," Butterworths, London (1981), discloses on pages 219, 220 and 227 reactions of trimethylsiloxyolefins and aromatic aldehydes in the presence of tetra-n-butylammonium fluoride, and Kita et al., Synthesis Comm., 1089 (1982) disclose reactions of [(1-methoxy-1-propenyl)oxy]trimethylsilane and ketones in the presence of tetra-n-butylammonium fluoride. Gostevskii et al., J. Organometallic Chem. 187, 157 (1980), describe cyanide or fluoride ion catalyzed reactions of trialkylsilanes and carbonyl compounds to form trialkylsilyl ethers. Delyagina et al., Izv. Akad. Nauk SSSR, Ser. Khim., No. 10, 2238 (1981), English language translation, disclose that the bifluoride ion source [(CH.sub.3).sub.2 N].sub.2 CH.sup..sym. HF.sub.2.sup..crclbar. adds more readily to fluoroolefins than conventional fluoride ion sources such as CsF or KF.
U.S. Pat. No. 3,637,630 discloses the use of fluorides and bifluorides as catalysts for preparing triazines from haloalkane nitriles and for cross-linking (curing) polymers containing cyanohaloalkyl groups. U.S. Pat. No. 3,917,542 discloses the use of ammonium hydrogen fluoride as a catalyst in the reaction of acrolein and ammonia to form pyridine and 3-methylpyridine. U.S. Pat. No. 4,017,518 discloses the use of acidic inorganic salts, including KHF.sub.2, as catalysts for preparing 4,4-dimethyldioxane-1,3 by reacting isobutylene and formaldehyde in aqueous medium. U.S. Pat. No. 4,266,064 discloses the preparation of a chloro-.beta.-trifluoromethylpyridine by reacting a chloro-.beta.-trichloromethylpyridine and HF in the presence of a selected metal fluoride or mixture thereof with ammonium fluoride or ammonium acid fluoride (NH.sub.4 F.HF). European Patent Application Publication No. 0 068 887, corresponding to U.S. patent application Ser. Nos. 389,110 and 389,111, discloses the polymerization of methacrylic and acrylic monomers, initiated by trialkylsilyl compounds and catalyzed by various nucleophilic anions, including fluoride and cyanide, selected Lewis acids, and bifluoride ions.